Conventionally, it has been known that norbornene-based monomers yield polymers by a metathesis polymerization reaction. In particular, there is employed a method of obtaining norbornene-based resin molded articles according to a so-called reaction injection molding (RIM) method in which polymerization and molding are simultaneously performed in one step in a die in the presence of a metathesis polymerization catalyst using a norbornene-based monomer which is cheaply available like dicyclopentadiene and the like.
In accordance with this RIM method, large molded articles can be attained using a cheap mold for low pressure molding and, further, the resulting molded articles have the good balance between rigidity and impact resistance. Accordingly, it can be said that the RIM method is one of highly practical molding means which can attain attractive molded articles. Particularly, in recent years, this method is expected to be applied to the uses of insulating substrate materials such as a printed circuit board, a laminate, copper foil with resin, a thin copper clad laminate, a polyimide film, a film for Tape Automated Bonding (TAB) and the like, and of sealing resins which seal the periphery of connecting portions in order to secure the strength of connection in the case of making electric connections between substrates or between a substrate and an electronic device.
However, even though uses, which needed higher rigidity and a lower linear expansion coefficient like this, increased and, correspondingly, enhanced rigidity and reduced linear expansion coefficient have been ever more required, these properties could not be adequately improved in balance by the conventional RIM method.
For this situation, various solving means have been proposed in order to achieve the enhanced rigidity and reduced linear expansion coefficient of the norbornene-based resin molded articles. An example of typical means may include a method of blending a reinforced fiber or a filler. For example, Japanese Kokai Publication Hei-10-17676 discloses a technique of obtaining a norbornene-based resin molded article by curing a norbornene-based resin composition which contains a particulate filler surface-treated in advance with a silane coupling agent, in the presence of a fiber reinforced material surface-treated in advance with a silane coupling agent. In accordance with this method, a molded article of the norbornene-based resin can be obtained with enhanced rigidity and reduced linear expansion coefficient. However, this method presented a problem that productivity would be deteriorated due to the necessity of surface treatment of the filler in advance and, also, a problem that when a filler was charged in a large amount, the norbornene-based resin composition would not flow well because of increased viscosity; therefore, compounded liquid would not flow every hole and corner of a mold. Further, it presented a problem that since air bubbles in the norbornene-based resin composition are hard to deaerate, mechanical properties of the molded article, particularly, mechanical strength is deteriorated.
Thus, it has been strongly required to develop a norbornene-based resin composition providing norbornene-based resin molded articles which have high fluidity and good mechanical properties even though blending conventional reinforced fiber or filler in a large amount.